Question

If the vagus branch of the frog is stimulated the heart will show
(a) Stoppage of heartbeat
(b) Decreased heartbeat
(c) Increased heartbeat
(d) No change

Answer 1

Hint: The vagus nerve mediates parasympathetic innervation of the heart. The vagus nerve explicitly serves to lower the heart rate. The right vagus innervates the node of the sinoatrial. Parasympathetic hyperstimulation is predisposed to bradyarrhythmias in those affected.

Complete answer:
The vagus nerve constitutes the tenth cranial nerve (X) . It is the cranial nerve that is the longest. (The name of it means "wanderer") . Most organs in the thoracic and abdominal cavities are supplied by it. This nerve also includes laryngeal (voice box) and pharyngeal motor fibers, as well as glands that produce digestive juices and other secretions. For such diverse activities as heart rate, gastrointestinal peristalsis, sweating, and quite a few muscle movements in the mouth, including speech, the vagus nerve is responsible. The vagus nerve partly regulates parasympathetic innervation of the heart and is shared by the thoracic ganglia. To be exact, the reduction of the heart rate is mediated by vagal and spinal ganglionic nerves.

Additional information: They are then divided into 3 major branches: the laryngeal nerves of the pharyngeal, superior, and recurrent. In order to join the rest of the vagus, fibers from the dorsal motor nucleus X pass through the spinal trigeminal nucleus and tract, emerging from the medulla oblongata lateral surface.
A vasovagal attack is a condition that causes the heart rate and blood pressure to drop rapidly, resulting in reduced blood flow to the brain and fainting. The most prevalent cause of fainting is a vasovagal attack. The condition is also known as neurocardiogenic syncope.
So, the correct answer is ‘(b) Decreased heartbeat’.

Note: When the vagus nerve is overstimulated, the blood vessels of the body, especially those in the lower extremities, dilate, and the heart slows down momentarily. The brain is deprived of oxygen, which causes the patient to lose memory.